Process of bright annealing steels and alloys



Patented Mar. 14', 1933 ROBERT JOHN OW'ENS Ali TD HUGH JOHN FRASER,

B OF

ASSIGNORS TO THE INTERNATIONAL NICKEL COMPANY, INC, 01' NEW YORK, N. Y

A CORPORATION OF DELAWARE PROCESS OF BRIGHT ANNEALING STEELS ALLOYS Ho Drawing.

The present invention relates to a process of bright annealing steels and alloys and parother nickel containing alloys may be an nealed in such a manner that the bri ht S111? face of the steel or alloy is not spoi ed.

It is another object of the present invention to provide a process of bright annealing metals and alloys having passive surfaces.

It is also within the contemplation of the present invention to provide an improved process of annealing metals and alloys without detrimentally affecting by oxidation the surface of the metal or alloys undergoing treatment.

It is a further object of the invention to provide a process of annealing metals and alloys which includes producing surface passivity on the metals and alloys for preventing detrimental discoloration by oxidation or the like.

Another object ofthe invention is the provision of controlling the relation between the character of the passive surface produced on the metal or alloy undergoing treatment and the nature ofthe' gaseous atmosphere for effecting bright annealing.

Other objects and advantages of the invention become apparent from the following description of a preferred procedure for carrying the invention into practice.

A metal or alloy such as a stainless-steel containing about 18% chromium and about 14% nickel or a nickel-chromium alloy containing about 88% nickel and about 12% chromium is fabricated in the customarymanner and has a bright surface imparted thereto by the usual operations. Although the metals or alloys may be in any desired condition, they are described herein as being in the form' of cold rolled sheets. These sheets are first made passive by a suitable process such as immersing them in a nitric .acid solution having about 5% to about 30% concentration. In practice, it has been found Application filed December 9, 1981. Serial No. 579,988.

0]! HUNTINGTON, WEST VIRGINIA,

160 F. to about 200 F. from about 15 min utes to about minutes. By heating the sheets in the foregoing manner, the surfaces thereof were rendered passive.

1he passive sheets are then washed and dr1ed in an.. ap ropriate manner. After washing and drymg, the passive sheets are placed in a suitable chamber such as a nickel,

linedmuflle furnace, which is provided with a gaseous reducing atmosphere, which is not.

necessarily completely free of water vapor. Various reducing gases may be employed but it s preferred to use completely dr1ed hydrogen.

period of about-2 hours to about 2 hours, the sheets were completely annealed without any detrimental discoloration occurring.

A specific example of carrying the invention into practice will now be better understanding of the invention by those skilled in the art.

Sheets of a nickel-chromium alloy containing about 88% nickel and about 12% chromium are immersed in about 10% nitricacid bath having. a temperature of about 180 .F. By keeping the sheets immersed for a period of about 45 minutes to about 1 ,hour, passivity is created on the surface of The thus passified sheets are the sheets. cleaned and dried.

By subjecting the dry passive sheets to heat treatment in a nickel lined electric mufie furnace having a reducing atmosphere such in thenickel lined electric furnace, ca ciumchloride driers were used in producing the By heating the sheets in the nickel lined electric furnace with a dry hydrogen atmosphere to a temperature oflabouti1650- to about 1800 F. or about 2000 F. for a given fora as hydrogen, or carbon monoxide and hydro I employed.

, It will be observed that by the use of the present invention alloys, such as the stainless steels and -nickel-chromium alloys, can be bright annealed in the form of sheets, strip,

etc. which is not commercially possible with the present facilities.

It will also be noted that in-carrying the present invention into practice, hydrogen ofexceptionally high purity is not necessarily a re uisite. eit er hydrogen or any of the gases derived by the burning or cracking of natural gas, other fuel gases, or fuel oils, providing free oxygen and sulphur compounds are not present, are adaptable to the process; it is not necessary to completely dry the gas, or gases. For the stainless steels, satisfactory results can be obtained with hydrogen containing water vapor as high as 1 grain per cubic foot. This has not been possible heretofore.

Furthermore, the present invention provides a process in which the capital expenditure and operating costs involved would be less than would be required to install and operate production units whose design would be based upon data heretofore available, if suclg units could be made commercially practica rocess which 0 ers a wide range of adaptaility insofar as handling alloys in various shapes and sizes is concerned.

It isalso within the contemplation of the invention to provide a method which provides eater ease of control of the operations than would be the case with prior art units and, consequently, the method can be handled by the ordinary run of mill labor.

Although the present invention has been described in connection with certain specific temperatures, reagents, gases, etc., it w1ll be observed that variations may be resorted to as those skilled in the art will understand and are to be considered within the scope of the appended claims. For instance, not only nickel and nickel alloys may be treated but also other metallic products such as stainless alloys, chromium steels, stellite, etc. Then again, in place of the nitric acid treatment, chromic acid treatment or electrolytic treatment can be used to make the surfaces passive. In the same way, various reducing atmospheres, such as, hydrogen-carbon monoxide or hydrogen, with or without nitrogen or other diluents and /or with or without carbon dioxide and water vapor. Furthermore, a nickel or nickel alloy or other suitable metallic heating chamber may be used instead of a nickel lined heating chamber.

What is claimed is:

or the nickel-chromium alloys,

recipes 1. The process ofannealing the sheet of stainless steel containing chromium and sheet passive, and then heating the said sheet to a temperature of about 1650 F. to about 1800 F. for several hours in the presence of a hydrogen containing gas to anneal said sheet without producing any substantial detrimental discoloration to the surface thereof.

2. The process of annealing the sheet of nickel-chromium alloy containing about 88% nickel and about 12% chromium which comprises rolling a sheet of said nickelchromium alloy, imparting a bright surface to said sheet, immersing said sheet in a nitric acid solution having about 5% to about 30% concentration, heating said sheet in said solution to a temperature of about 160 F. to about 200 F. from a period of about 15 minutes to about 60 minutes to make the said sheet passive, and then heating the said sheet to a temperature of about 1650 F. to about 1800 F. for several hours in the presence of a hydrogen containing gas to anneal said sheet without producing any substantial detrimental discoloration to the surface thereof. Moreover, the resent invention provldes a 3. The process of annealing a product from the group consisting of nickel stainless steel and nickel-chromium alloys with a bright surface which comprises forming the aforeature of about 1650 F. to about 2000 F.

for several hours in the presence of a reducing atmosphere to anneal said product without producing any substantial discoloration of the bright surface.

4. The process of annealing a product from the group consisting of nickel stainless steel and nickel-chromium alloys with a bright surface which comprises forming a product of nickel alloy, imparting a bright surface to said product, treating said product with a nitric acid solution capable of rendering the bright surface passive and then heating saidproduct to a temperature of about 1650 F. to about 2000 F. for a period of time up to about 2 hours in the presence of a reducing atmosphere to anneal said sheet without producing any substantial discoloration of the bright surface.

5. The process of annealing a sheet from the group consisting of nickel stainless steel and nickel-chromium alloys with a bright surface which comprises rolling a sheet of nickel alloy, imparting a bright surfaceto said sheet, treating said sheet with a hot nitric acid solution to render said bri ht surface passive, and then heating the suit? sheet with a passive surface to atemperature of about 1650 F. to about 2000 F. for several hours in the presence of a reducing atmosphere without reducing any substantial detrlmental disco oration to the bright surface.

In testimony whereof, we have hereunto set our hands.

ROBERT JOHN OWENS. HUGH JOHN FRASER. 

